The present invention refers to a threaded connection for connecting components to pipes, and more particularly, for connecting those components which are tapped on double-walled pipes.
One object of the present invention is to provide a threaded connection with a redundant barrier, in order to ensure the sealing of the connection such that no leakage is spilled from the pipe.
Another object of this invention is to provide a threaded connection suitable for being used in aircraft fuel installations which comprise fuel pipes designed as double-walled pipes for running along pressurized areas.
Another object of this invention is to provide a simplified threaded connection with a reduced number of components, entailing a weight reduction and an easiest installation. The threaded connection additionally achieves simplified maintenance.
There are already known threaded connections that provide sealing after their threading through different sealing arrangements. Typical sealing arrangements are provided by means of sealing rings, such as O-rings, or by complementary surfaces that perfectly fit each other avoiding the pass of fluid.
European Patent Application EP0829670A2 discloses an exemplary use of O-rings to provide sealing. That Application describes a hose coupler that attaches in a manner that provides a sealed conduit for preventing bacteria or other contaminants being present at the coupler connection. That Application describes a hollow female coupler piece connected with a hollow male coupler piece through an intermediate connector piece, wherein the coupler also includes means for sealing. This means for sealing includes an O-ring compressed by a shoulder of the male coupler against one or both of the intermediate and the second end of the female coupler piece when the male coupler piece is threadedly interconnected to the female coupler piece via the intermediate connector. So, either the second end of the female coupler piece, the intermediate piece or a combination thereof includes an annular groove defined therein to receive the O-ring. However, that Application does not provide a connection with a redundant barrier.
U.S. Pat. No. 5,127,679A discloses an exemplary use of complementary surfaces to provide sealing. That patent describes a fluid-tight connector that comprises two members with respectively concave and convex co-operating mating ends, joined together by an internally threaded sleeve retaining one of the members and tightened by being screwed onto the other part. By this configuration, the connector defines a conical contact surface that matches perfectly acting as a barrier for fluid loss. Again, that patent does not provide a connection with a redundant barrier.
In aeronautical field there also exists the need of providing a threaded connection with a redundant barrier. As known, aircraft fuel installations must comprise double-walled fuel pipes for running along pressurized areas. Conventionally, each double-walled fuel pipe comprises an outer pipe covering an inner pipe that conveys the fuel in order to ensure that no leakage from the inner pipe will be spilled.
Currently, to fulfill with international airworthiness regulations, components fixed on double-walled pipes by tapping on them must ensure a redundant barrier on the connection.
Installing components, such as pressure or temperature sensors, tapped on an inner pipe, requires a special interface on the component which complicates the connection at the time that demands certain space for its installation or accommodation in the connection.
To comply with the double barrier requirement in this type of connections, it becomes necessary to purchase dedicated components, usually not standardized, equipped with a tedious system of flanges, rings and bolted connections, which increases the time required for fixing components and the weight of the resulting connection.
Another solution consists of giving up the compliance of the double barrier requirement just on the connection. However, this solution is not acceptable in most of the cases, and especially as a permanent solution.
FIG. 1 shows a longitudinal section of a prior art sensing element 27 connected to the inner pipe 29 of a conventional double-walled pipe, such double-walled pipe is formed by an inner pipe 29 shrouded by an outer pipe 28. In the embodiment of the figure, the element connection 30 is directly threaded to the inner pipe 29, providing only one barrier 31 for sealing the connection. The arrows depicted in the figure show potential paths for fluid leaking so that, just providing one single barrier, other paths for fluid are let unsealed.
Considering FIG. 1, an option for providing a redundant barrier could consist of including sealing interfaces 32, 33 in the sensing element 27, therefore the redundant barrier requirement would be fulfilled. However, the connection of the sensing element would require several bolts and nuts, adding weight, making the installation more complex and taking up more room for the connection.
Therefore, it has been detected in this technical field the need for a threaded connection that provides redundant sealing barriers, especially needed in the aeronautical industry to fulfill with the international airworthiness regulations. It is also needed that the threaded connection provides a reduced number of components, simplifying the connection at the same time that achieves a reduction in weight.